Hi Franz,
The thickness of the frame around the window will drive how many bolts
are needed to seat and seal the o-ring properly. We will come up with a
reasonable thickness based on this. Richards idea ov pivoting the
hodoscope away from the window during maintenance deserves some thought.
Cheers,
tim
Franz Klein wrote:
Tim and Richard,
last Friday James showed me the design drawing. My initial worry that
we won't have more clearance but 2.8cm (for largest scintillator) was
based on the pdf file James sent around on 1/22. However, the vacuum
chamber drawing is largely conceptual: the flange for the long window
is 1" thick and not detailed. It is more realistic to assume a 1/4"
plate as flange, which gives enough space for a cover plate (which will
be suspended from above and fall into a grooved beam).
Greetings
Franz
On Wed, 4 Feb 2009, Tim Whitlatch wrote:
Thanks Richard.
Yes we are talking about shrinking the vacuum chamber. Right now we
have about 3cm. We can make due with this but do not have an easy way
for vacuum sealed plate. I do not think this is required, but hearing
protection would be required to work in the area at all times.
Tim
Richard Jones wrote:
Tim,
If you mean 20cm of open space normal to the window, I don't think we
want that much distance between the window and the detectors. At a
crossing angle of 10 degrees, that would mean more than 1m of electron
trajectory after the window. Of course, we are talking about shrinking
the vacuum chamber by 20cm, not moving the focal plane by 20cm, right?
Yang can tell you that moving the focal plane is a much bigger job!
You could gain that space by shrinking the vacuum chamber, but it would
affect our resolution. We could simulate it, but I am pretty sure that
the effect would be significant degradation in the resolution.
Richard Jones
Tim Whitlatch wrote:
Hi all,
How critical is the spacing (air gap) between the hodoscope
scintillators and the vacuum window? Is 20 cm ok to allow a mechanism
for a window cover during maintenance? If not, we will have to slide
the protective plate over the window.
Thanks,
Tim
===============================================================
Franz J. Klein, Associate Professor
CUA, Department of Physics
Washington, DC 20064
office: Hannan Hall 206 phone: 202-319-6190
or: Jefferson Lab,CC F-243 phone: 757-269-6671
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